Dahlias offer spectacular color for the late-summer garden. They're fairly easy to grow if you give them what they like -- sun, well-drained soil and a low-nitrogen fertilizer -- and keep the slugs off them.
PLANTING:
In western Oregon, you can plant dahlias from mid-April through June, but the earlier the better. Plant in well-drained soil in full sun when the soil is dry enough to work. Plant the tubers with the growing eyes up, 4 to 6 inches deep and 18 to 24 inches apart. Put a small handful of bone meal in the hole first and work in well.
Don't water after planting; spring soil is moist enough to encourage sprouting.
Don't use a bark mulch on dahlia beds. It doesn't allow the soil to get warm enough, and it increases the soil's acidity, which discourages dahlias.
WATER:
Spring rains will take care of watering needs until dry weather arrives. During summer, water deeply once or twice a week.
FEEDING:
Dahlias don't like too much nitrogen. They'll get leggy and have weak stems and small blooms. Avoid mushroom compost, fish fertilizers and water-soluble fertilizers because they are usually high in nitrogen. Choose a fertilizer with a low first number (representing nitrogen), such as 5-10-10 or 10-20-20 or even a combination with 0 as its first number. Vegetable fertilizers, particularly tomato fertilizers, are good. The second and third numbers refer to phosphorus and potassium, which promote stiff stems and good root growth. Apply fertilizer a few weeks after planting and feed again lightly about the first of July. Don't overfeed.
PESTS:
Slugs love to chomp on the tender new shoots, so use a slug bait, trap or copper barrier. To prevent mildew, try dousing or spraying with a mixture of 1 tablespoon light horticultural oil and 1 tablespoon baking soda to 1 gallon of water. If you have gopher trouble, bury a piece of chicken wire when you plant tubers. Dig the hole deeper than normal, make a basket of chicken wire, and have it extend about 3 inches aboveground. Fill in with soil and plant the tuber as usual.
STAKING:
Put in stakes when you plant dahlias to prevent piercing the tuber later. Tomato cages work well to support dahlias, and the foliage is thick enough to hide them. Or try this trick (see the
): When the plants are almost knee-high, cut them off to 18 inches or so. This makes them bushier and their stems stronger, so they don't need stakes if they're growing in full sun. However, Swan Island Dahlias advises staking any dahlias that will reach 3 feet or taller.
PINCHING:
To promote shorter, bushier plants with better stems for cutting, pinch or cut the center shoot just above the third set of leaves.
WINTER CARE:
Dig dahlias after the first hard frost knocks them down. Before digging, cut stalks to about 6 inches. Gently lift tubers from soil with a spade, being careful not to break the necks. Wash off dirt and allow them to air-dry, not in direct sun. Pack tubers in crates or cardboard boxes lined with 10 layers of newspaper. Pack in sand, peat moss or dry sawdust. Never store in sealed plastic bags because the tubers will rot. Keep in a cool, dry area -- 40 to 45 degrees is best. Check a couple of times during winter and discard any rotted tubers.
DIVIDE:
In fall or spring. It's easiest to see the growing eyes in spring. Tuber size doesn't affect plant size. Even the smallest tuber will produce a full-size plant if it has a live eye. Snap or cut tubers with eyes from the main stem. Cut surfaces should be allowed to dry overnight before planting or storing.
CUT FLOWERS:
After cutting blooms, put the stems in 2 to 3 inches of very hot water (about 160 degrees) and let cool for several hours or overnight. This sets the blooms, which will last four to six days in arrangements.
Source: Nicholas and Linda Gitts, Swan Island Dahlias
WANT MORE?
The
at
in Canby is Aug. 27-29 and Sept. 3-5. Indoor display hours are 10 a.m.-6 p.m. Field hours are 8 a.m.-6 p.m. Admission and parking are free, and the event is wheelchair-accessible.
Or
Aug. 1 through September, open daily 8 a.m.-6 p.m., with picnic tables available for those who bring a picnic lunch.
This year's
open to current Swan Island Dahlias customers, has a Sept. 15 deadline for entries. You can also see winning photos from the 2010 contest.
on growing, storing, dividiing, etc.
in Portland has
on planting, harvest and storage, cuttings and more.
The American Dahlia Society lists
, as well as
including lists of the best dahlias of specified type and color.
Kym Pokorny gives tips on
-- Homes & Gardens staff
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